Research has shown maternal diet (e.g. fish) and nutrient intake (e.g. Fe, folate, n-3 fatty acids) to be extremely important for healthy birth outcomes and post-natal neurodevelopment. At the same time, studies have shown the health and neurodevelopment of the fetus to be exquisitely sensitive to neurotoxic environmental toxicants; classic examples include methylmercury (MeHg) and lead (Pb). Despite growing evidence that the potential adverse effect(s) of neurotoxic chemicals may be exacerbated by poor nutrition, or blocked by proper nutrition, for most neurotoxic chemicals there are no detailed human studies of such diet-toxicant interactions. Here such a study is proposed for both classic (heavy metals) and emerging (BPA and phthalates) environmental neurotoxicant exposures in an established prospective Canadian birth cohort (APrON), whereby detailed nutritional measurements are available for assessing such interactions on early childhood behavior and cognitive development. The interplay between various toxicants, between diet and toxicant, and between nutrients and toxicants will be evaluated for cognitive, language, motor, emotional and behavioral measures of child development. Various other modifiers including maternal mental health, maternal physical activity and weight gain are also available for statistical modeling. It is anticipated that the results of this unique study will inform preventio strategies to help mitigate the harmful effects of classic and emerging environmental developmental neurotoxicants. PUBLIC HEALTH RELEVANCE: Research has shown maternal diet and nutrient intake to be extremely important for healthy neurodevelopment. At the same time, studies have shown the health and neurodevelopment of the fetus to be exquisitely sensitive to neurotoxic environmental toxicants; a classic example is methyl mercury. Despite growing evidence that the potential adverse effect(s) of neurotoxic chemicals may be exacerbated by poor nutrition, or blocked by proper nutrition, for most neurotoxic chemicals there are no detailed human studies of such diet-toxicant interactions. Here we propose such a study for both classic and emerging environmental neurotoxicant exposures in an established prospective birth cohort, whereby detailed nutritional measurements are available for assessing such interactions on behavior, temperament, and cognitive development.